Groundwater Level Study

A study of the groundwater levels in the Mine Brook aquifer was done during 4 years (1995 - a dry year, 1998 - a wet year, 1999 - a normal year, and 2000 - a normal year).  Weekly or biweekly groundwater level measurements were taken at 2 points in the Mine Brook aquifer.  The groundwater measurements were taken at test well 7-2 and test well 10-2.  These test wells were chosen because they were a substantial distance from active municipal wells (test well 7-2 is approx. 1,600 ft from Mine Brook Well #3,  and test well 10-2 is approx. 2,400 ft from Mine Brook Well #3) and therefore would be beyond the normal cone of pumping influence.  Measurements were taken by dropping a weighted tape measure down the test well until the tape made contact with the surface of the groundwater in the well - the measurement is from the groundwater surface to the top of the test well.

The year 1995 was a relatively dry year, the Mine Brook stopped flowing by Mine Brook Well #2 on July 1st, and did not start flowing again until October 28th.  During the late summer in 1995, the Mine Brook became a series of puddles.

The year 1998 was a very wet year, the Mine Brook flowed as a stream the entire year.  During the later spring and early summer, heavy rainfalls caused the groundwater levels to surcharge from the test well 7-2 (the elevation of the groundwater in upper reaches of the aquifer exceeded the elevation of the top of the test well at location 7-2).

The years 1999 and 2000 had close to normal rainfall and the Mine Brook was seen flowing in all but one measurement period.

The following links show graphs of the levels of the groundwater for the 4 years that measurements were made (plus the rainfall during the previous week).  You will notice that the groundwater levels are high in the spring, then fall until September when they start to climb once again - deviations from this pattern can be seen when we have very heavy rainfalls (particularly 1998).  Much of this normal pattern can be attributed to a) the vegetation in the area comes out of dormancy in the spring and starts to take up much of the rain water, and then goes dormant again in the fall, when more of the rainfall can reach the groundwater, and b) the summer's higher temperatures increase the amount of rainfall that evaporates rather than soaking into the ground.

• Chart of Groundwater Levels in Mine Brook Aquifer - 1995
• Chart of Groundwater Levels in Mine Brook Aquifer - 1998
• Chart of Groundwater Levels in Mine Brook Aquifer - 1999
• Chart of Groundwater Levels in Mine Brook Aquifer - 2000

Table of Rainfall Amounts in Walpole